System for detecting offset printing using same

Abstract

The invention concerns a detection system ( 7 ) for measuring at least one characteristic of an inked zone ( 5 ) comprising at least one sensor adapted to sense a light radiation reflected by said inked zone ( 5 ) and to generate a measurement signal representing at least the characteristic of the inked zone ( 5 ). Such a system further comprises at least one first optic fiber ( 10 ), adapted to convey up to the neighborhood of the inked zone ( 5 ), a light radiation emitted by a light source ( 11 ).

1. An assembly of a multiplicity of machines employed to perform a printing operation,
 where the said assembly has a single light source, with each machine including: 
 a printing device that creates at least one inked zone ( 5 ) on a printing substrate, by means of at least one printing ink, 
 a feedback loop ( 6 ) to perform the regulation of at least one characteristic of said inked zone ( 5 ), the feedback loop acting directly on the printing device; wherein the feedback loop includes:
 at least one control unit, to control at least one characteristic of the said printing ink, in accordance with a difference between at least one characteristic of a control inked zone ( 5 ) and at least one characteristic of a measured inked zone ( 5 ); 
 at least one detection system ( 7 ) to measure at least one characteristic of said inked zone ( 5 ), where the detection system ( 7 ) includes: at least one sensor designed to capture light radiation reflected by the said inked zone ( 5 ), and to generate a signal representing at least the characteristic of the inked zone ( 5 ), and 
 at least one first optical fibre ( 10 ), designed to convey, to the vicinity of the inked zone ( 5 ), light radiation emitted by the said single light source. 
 
 
     
     
       2. An assembly of machines according to  claim 1 , in which a part of each sensor is common to all of the machines. 
     
     
       3. An assembly of machines according to  claim 1 , in which the measured signal representing the characteristic of the inked zone includes a signal representing the colour, which itself includes at least a part of the light radiation reflected by the inked zone ( 5 ). 
     
     
       4. An assembly of machines according to  claim 1 , in which the detection system of each machine also includes at least one second optical fibre ( 12 ) to convey the said signal representing the colour of the inked zone ( 5 ) from the vicinity of the inked zone. 
     
     
       5. An assembly of machines according to  claim 1 , in which the sensor includes a spectrophotometer ( 13 ). 
     
     
       6. An assembly of machines according to  claim 1 , in which the inked zone ( 5 ) includes a printed copy and an adjusting strip for an offset type printing process, the adjusting strip being located on a margin of the printed copy, and in which the printing device is a printer of the offset type. 
     
     
       7. An assembly of machines according to either of  claim 1  or  6 , in which the characteristic of the control inked zone is obtained from a test piece by means of the said detection system ( 7 ). 
     
     
       8. An assembly of machines according to  claim 1 , including a single control unit shared by all of the feedback loops ( 6 ) of the said machines. 
     
     
       9. An assembly of machines according to  claim 8 , that also includes at least one second optical fibre ( 12 ) designed to convey, from the vicinity of the inked zone ( 5 ), light radiation reflected by the inked zone ( 5 ), and in which the signal representing the brightness includes a signal representing the intensity of the reflected light radiation. 
     
     
       10. An assembly of machines according to  claim 1 , in which the measured signal representing the characteristic of the inked zone includes a signal representing the brightness of the inked zone ( 5 ), where the detection system has at least one second optical fibre ( 12 ) designed to convey from the vicinity of the inked zone ( 5 ), light radiation reflected by the inked zone ( 5 ). 
     
     
       11. An assembly of machines according to  claim 10 , in which the first optical fibre ( 10 ) is designed to illuminate the inked zone ( 5 ) at least to the vicinity of a point of incidence on a lighting axis,
 and in which the at least one sensor of light radiation reflected by the said inked zone ( 5 ) is positioned more-or-less on a reception axis, with the said reception axis being more-or-less symmetrical with the lighting axis, with an axial symmetry along a straight line N passing through the said point of incidence, and orthogonal to the said inked zone ( 5 ). 
 
     
     
       12. An assembly of machines according to  claim 11 , in which the lighting axis and the reception axis are more-or-less orthogonal to the said inked zone ( 5 ). 
     
     
       13. An assembly of machines according to  claim 1 , in which the sensor also includes at least one camera ( 12   a ) and in which the signal representing the brightness is a signal representing the spatial extension and/or the intensity of the reflected light radiation. 
     
     
       14. An assembly of machines according to  claim 13 , in which the sensor includes digital processing means to obtain the signal representing the brightness, from an image acquired by the camera.